1. Field of the Invention
The present invention relates to an apparatus for detecting, for example, angular rotational positions of the crankshaft of an engine in an automobile, and more particularly to a rotation detecting apparatus capable of detecting a reference angular position and rotational angles of a rotating object such as the crankshaft of an engine without any delay irrespective of its rotational speeds.
2. Description of the Prior Art
The apparatus heretofore known for detecting the rotation of the crankshaft of an automobile engine includes an apparatus in which a magnetic member having a coil wound thereon is positioned opposite to a rotational member and an alternating electromotive force is induced in the coil in response to the magnetic flux variations in the projections on the magnetic member.
However, this type of apparatus is disadvantageous in that the alternating electromotive force induced in the coil is affected by the magnetic flux variations, that is, by the rotational speeds of the rotational member. If the speed of the rotational member is low, practically no alternating electromotive force is induced in the coil, which makes it impossible to detect the rotation of the rotational member. If the speed of the rotational member increases, the inductance of the coil gives rise to a delay in the detection of the rotation of the rotational member.
Another disadvantage is that, where the detection of rotational angle signals and a reference angular position signal is required, it is necessary to provide separate corresponding projections on the rotational member and detecting means at two places, which makes the construction of the rotation detecting apparatus complicated. The present invention is intended to overcome the foregoing deficiencies of the prior art.